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c# için mesela

private void CreateMyTopMostForm()
{
// Create lower form to display.
Form bottomForm = new Form();
// Display the lower form Maximized to demonstrate effect of TopMost property.
bottomForm.WindowState = FormWindowState.Maximized;
// Display the bottom form.
bottomForm.Show();
// Create the top most form.
Form topMostForm = new Form();
// Set the size of the form larger than the default size.
topMostForm.Size = new Size(300,300);
// Set the position of the top most form to center of screen.
topMostForm.StartPosition = FormStartPosition.CenterScreen;
// Display the form as top most form.
topMostForm.TopMost = true;
topMostForm.Show();
}